Intro

• Bash stands for Bourne Again SHell
• Most sh scripts can be run by Bash without modification.
• A variable’s name is a string starting with a letter and containing letters, numbers, or underscores
• Putting spaces around the equal sign will cause errors

executing a file

• Create a file test.sh -add

  echo "hello world"
  

  -run bash test.sh

sh commands

use echo to print the commands

variables

var=2021  
var1="Fisat"
sem="4"  - create a variable
	never add space | its an error

echo $sem - use $ to take the value

quotes

var=5

echo “$var” is same as $var

echo ‘$var’

prints $var instead of 5

command line arg

var1=$1

var2=$2

adding

((var3=var1+1))

((var4=var2+2))

echo $var1

echo $var2

call bash test.sh 10 32

conditional

if

var1=$1
var2=$2

if [[ $var2 -gt $var1 ]]
then
	echo "$var2 greater than $var"
else
	echo "$var2 lesser than $var"
fi

fi - tells that the if is done can use if((var2>var1)) also

for

sum=0
for((i=0;i<10;i++))
do
	((sum=sum+i))
done
echo $sum

while

sum=0
i=0
while((i<10))
do
	((sum=sum+i))
	((i=i+1))
done
echo $sum

File Handling

if[[ -e "echoooo.png" ]]
then
	echo "File exists"
else
	echo "No file"
fi

while read line
do
	echo  $line
done<"test.txt"

grep - find the word

eg: grep "hello" test.txt find the hello from test.txt ``` grep “hello” test.txt

grep -i “hello” test.txt #case insensitive

grep -i “<hello>” test.txt #only ` hello ` space after and before ```